HK4: Heckler & Koch's Multi-Caliber Pocket Pistol
The Heckler & Koch HK4 is a unique multi-caliber pocket pistol developed in 1966 and released in 1968. It could fire .22 LR, .25 ACP, .32 ACP, and .380 ACP rounds through interchangeable barrel and magazine kits. While innovative, its complex rimfire conversion and commercial competition from the Walther PPK limited its market success, despite a significant contract with the German Customs Police.









